In vertebrate animals, retinal neural circuits process images, extracting information about color, shape size and movement from visual surroundings. While laboratory animals such as cat, rat, mouse and rabbit provide plausible models of human nocturnal vision, zebrafish, like humans and other old-world primates, are remarkable for diurnal color vision. Zebrafish is a tetrachromat with 4 cone photoreceptor types selectively sensitive to red, green, blue and ultraviolet wavelengths. Studies of the neural circuitry through which this rich color information is processed can be aided through studies of fish lines with additional special-purpose genes. The zebrafish lines generated and maintained under this protocol were imported from other laboratories, where extra genes were added to, or deleted from, the DNA. In some cases new phenotypes are created in house by cross breeding. Adult and larval fish produced in this research program are studied according to goals and objectives described in other research programs.